The present invention relates to a rear wheel steering device.
There have been devised and demonstrated various types of steering systems which can turn the rear wheels in combination with the turning of the front wheels as disclosed in Japanese Utility Model Laid-Open Publication No. 60-66581.
In the case of the steering systems of the type which turn the rear wheels in combination with the front wheels, most of the rear wheel steering devices are such that a gear train or mechanism of as the rack-pinion type is utilized same as the front wheel steering device, so that the gear train or mechanism is operated in combination with the steering operation of the front wheel steering device, whereby the rear wheels rotate about their corresponding king pins.
However, the conventional rear wheel steering devices of the type described above have the drawbacks that the device has a complex construction; the production cost is great; and a considerably large space is required for the installation of the rear wheel steering device.
Furthermore, the turning angle of the rear wheels is extremely smaller than that of the front wheels. When the rear wheel, steering operation is carried out by the gear train or mechanism of the type described above or a linkage, backlash between the engaging gears or play of the linkage adversely affects the control of the steering of the rear wheels. Therefore there arise the drawbacks that the gears and links must be manufactured with a high degree of accuracy; that backlash and play must be reduced to a minimum; and that productivity is considerably low.
In the case of directly steering the rear wheels by means of hydraulic actuator, an electric motor or the like, it becomes very difficult to correctly control a very small turning angle of the rear wheels by the actuator itself. Furthermore, there exists the drawback that it is very difficult to maintain the turning angle of the rear wheels by the actuator alone.